ASA 124th Meeting New Orleans 1992 October

1aPA1. The limitation of ultrasonic flaw sizing by a model-based approach.

A simple model has been developed that accounts for the excitation signal
to the transducer, the transducer characteristics, and the diffraction of the
sound for the purpose of flaw sizing. The goal has been to seek the ramp
response that is the second integral of the impulse response. The ramp response
yields volume and cross-sectional area information about the flaw. This
research has demonstrated that all of the above mechanisms are high-pass
frequency filters whereas the frequency content needed for the ramp response is
low, namely ka<2. Unfortunately the physical mechanisms reduce the
low-frequency content well below the noise levels and it is impossible to
extract the information required even though the transducer is driven with a
signal that contains a large amount of low-frequency content.